Supported catalyst

ABSTRACT

The invention provides a supported chromium catalyst system comprising a chromium catalyst precursor bound via at least one heteroatom to a functionalised support, said heteroatom being connected to said support via an organic group.

[0001] This invention relates to a new supported catalyst system capableof producing polyolefins having a broad or narrow molecular weightdistribution, and in particular to a chromium catalyst precursorsupported on a functionalised carrier.

[0002] The use of chromium catalysis for the polymerisation of olefinsis well established in the art. Whilst these catalysts may be usedalone, conventionally chromium catalysts, e.g. chromium oxides aresupported on a carrier, e.g. an oxide support such as silica or alumina.Such supported catalyst systems are used either without a cocatalyst orwith a metal alkyl cocatalyst as is well known in the art.

[0003] In the polymerisation of ethylene, all known supported chromiumcatalysts of the type hereinbefore described give rise to polyethylenewith a broad molecular weight distribution. Such polyethylenes maycomprise low molecular weight fractions that may give rise to unwantedsmell and/or very high molecular weight components that may cause theformation of inhomogeneous gels in the polymer product.

[0004] It would therefore be desirable if a product having a narrowmolecular weight distribution could be prepared using chromium catalysisto alleviate the problems discussed above. Also, it would be desirableif a catalyst system could be found which allowed the production ofpolymers with varying Mw/Mn values simply by varying the nature of thesupport.

[0005] It has now been surprisingly found that by supporting chromiumcatalyst precursors on certain functionalised polymer supports, a broador narrow molecular weight polyolefin product may ultimately be produceddepending on the nature of the functionalised support. The polymersupport may for example be a functionalised polystyrene as described inU.S. Pat. No. 4,623,707. This Patent teaches the use of a functionalisedpolystyrene carrier in supporting a Ziegler-Natta catalyst and is hereinincorporated by reference. However, whilst the functionalised. supportshave previously been described, never before have they been proposed foruse with chromium catalyst precursors allowing the formation ofpolyolefins having tailorable molecular weight distributions.

[0006] Thus, viewed from one aspect the invention provides a supportedchromium catalyst system comprising a chromium catalyst bound via atleast one heteroatom, e.g. a nitrogen, sulphur, phosphorus or oxygenatom, to a functionalised support, said heteroatom being connected tosaid support via an organic group.

[0007] Viewed from another aspect the invention provides a process forthe preparation of a supported chromium catalyst system comprising:

[0008] (I) reacting a chromium catalyst precursor with a functionalisedsupport in a solvent to bind said chromium catalyst precursor to saidfunctionalised support via at least one heteroatom, e.g. a nitrogen,sulphur or oxygen atom, attached to said support via an organic group;and

[0009] (II) recovering a supported catalyst as a free-flowing solid orslurry.

[0010] Viewed from yet another aspect the invention provides the use ofa supported catalyst system as hereinbefore described in thepolymerisation of olefins.

[0011] Viewed from still yet another aspect the invention provides amethod of polymerisation comprising polymerising at least one olefin inthe presence of a supported catalyst system as hereinbefore described.

[0012] Viewed from a yet further aspect the invention providespolyolefins prepared using the supported chromium catalyst system ashereinbefore described.

[0013] The supported catalyst of the invention comprises a chromiumcatalyst bound to the functionalised support via a heteroatom. This isachieved by reacting a chromium catalyst precursor with thefunctionalised support. The chromium catalyst precursor may be selectedfrom a wide variety of suitable precursors but must be a precursorcapable of forming at least one bond, e.g. 1 to 3 bonds with theheteroatoms connected to the surface of the functionalised support.Suitable precursors will be readily determined by the person skilled inthe art.

[0014] In one embodiment, the chromium catalyst precursor should carryat least one, e.g. two groups which are capable of being displaced bythe heteroatoms present on the support. Suitable leaving groups will bereadily determined by the artisan. For example, suitable chromiumcatalyst precursors include those of formula (I)

CrA_(x)B_(y)  (I)

[0015] wherein each A independently represents any group or groups whichremain bound to the chromium after contact with the support e.g. anη-ligand, for example an open chain η³, η⁴ or η⁵ ligand or a closedringη⁵ ligand such as cyclopentadienyl, indenyl, or fluorenyl ligand, oran oxo group;

[0016] each B independently represents a leaving group such as halogen(e.g. chlorine, bromine or iodine, especially chlorine), alkenyl (e.g.allyl or 2-methyl allyl), siloxy, alkyl, alkoxy, amido andcyclopentadienyl;

[0017] x is an integer of 1 or 2; and

[0018] y is an integer of 1 or 2 wherein x+y is 3.

[0019] By leaving group is meant a group which is capable of beingdisplaced by a heteroatom attached via an organic group to the support.

[0020] Alternatively, the chromium catalyst precursor may be of formula(II)

CrD₄  (II)

[0021] wherein each D independently represents alkyl, siloxy, alkoxide,oxo, halo, aryl, e.g. phenyl.

[0022] Alternatively, the chromium catalyst precursor may have at leastone, e.g. two free coordination sites to allow the formation of one ormore bonds between the chromium catalyst precursor and the heteroatomspresent on the support without any displacement taking place. Suitablesuch species include a Cr(η-ligand)₂ or CrD(η-ligand) precursor where Dis as hereinbefore defined and the η-bonding ligands which may be thesame or different may, for example, be of formula III

CPY_(m)  (III)

[0023] where Cp is an unsubstituted, mono-substituted or polysubstitutedhomo or heterocyclic cyclopentadienyl, indenyl, tetrahydroindenyl,fluorenyl, benzindenyl, cyclopenta[l] phenanthrenyl, azulenyl, oroctahydrofluorenyl ligand or a heterocyclic analog thereof, e.g.containing a ring nitrogen, boron, sulphur or phosphorus; m is zero oran integer having a value of 1, 2, 3, 4 or 5; and where present each Ywhich may be the same or different is a substituent attached to a ringatom of Cp and selected from halogen atoms, and alkyl, alkenyl, aryl,aralkyl, alkoxy, alkylthio, alkylamino, (alkyl)₂P, siloxy (e.g.alkylsiloxy), germyloxy (e.g. alkylgermyloxy), acyl and acyloxy groupsor one Y comprises an atom or group providing an atom chain comprising 1to 4 atoms selected from C, O, S, N, Si, Ge and P, especially C and Si(e.g. an ethylene group) to a second η-ligand of formula II, e.g. anunsubstituted, mono-substituted or polysubstituted homo or heterocycliccyclopentadienyl, indenyl, tetrahydroindenyl, fluorenyl oroctahydrofluorenyl ligand group.

[0024] In the compounds described herein unless otherwise specified anyhydrocarbyl moiety preferably contains up to 20 carbon atoms, morepreferably up to 10 carbons, especially up to 6 carbons.

[0025] In the η-bonding ligands of formula II, the rings fused to thehomo or hetero cyclopentadienyl rings may themselves be optionallysubstituted e.g. by halogen atoms or hydrocarbyl groups containing 1 to20 carbon atoms.

[0026] Many examples of such η-bonding ligands and their synthesis areknown from the literature, see for example: Möhring et al. J. Organomet.Chem 479:1-29 (1994), Brintzinger et al. Angew. Chem. Int. Ed. Engl.34:1143-1170 (1995).

[0027] Examples of suitable η-bonding ligands include the following:

[0028] cyclopentadienyl, indenyl, fluorenyl,pentamethyl-cyclopentadienyl, methyl-cyclopentadienyl,1,3-di-methyl-cyclopentadienyl, i-propyl-cyclopentadienyl,1,3-di-i-propyl-cyclopentadienyl, n-butyl-cyclopentadienyl,1,3-di-n-butyl-cyclopentadienyl, t-butyl-cyclopentadienyl,1,3-di-t-butyl-cyclopentadienyl, trimethylsilyl-cyclopentadienyl,1,3-di-trimethylsilyl-cyclopentadienyl, benzyl-cyclopentadienyl,1,3-di-benzyl-cyclopentadienyl phenyl-cyclopentadienyl,1,3-di-phenyl-cyclopentadienyl, naphthyl-cyclopentadienyl,1,3-di-naphthyl-cyclopentadienyl, 1-methyl-indenyl,1,3,4-tri-methyl-cyclopentadienyl, 1-i-propyl-indenyl,1,3,4-tri-i-propyl-cyclopentadienyl, 1-n-butyl-indenyl,1,3,4-tri-n-butyl-cyclopentadienyl, 1-t-butyl-indenyl,1,3,4-tri-t-butyl-cyclopentadienyl, 1-trimethylsilyl-indenyl,1,3,4-tri-trimethylsilyl-cyclopentadienyl, 1-benzyl-indenyl,1,3,4-tri-benzyl-cyclopentadienyl, 1-phenyl-indenyl,1,3,4-tri-phenyl-cyclopentadienyl, 1-naphthyl-indeny,1,3,4-tri-naphthyl-cyclopentadienyl, 1,4-di-methyl-indenyl,1,4-di-i-propyl-indenyl 1,4-di-n-butyl-indenyl, 1,4-di-t-butyl-indenyl,1,4-di-trimethylsilyl-indenyl, 1,4-di-benzyl-indenyl,1,4-di-phenyl-indenyl, 1,4-di-naphthyl-indenyl, methyl-fluorenyl,i-propyl-fluorenyl, n-butyl-fluorenyl, t-butyl-fluorenyl,trimethylsilyl-fluorenyl, benzyl-fluorenyl, phenyl-fluorenyl,naphthyl-fluorenyl, 5,8-di-methyl-fluorenyl, 5,8-di-i-propyl-fluorenyl,5,8-di-n-butyl-fluorenyl, 5,8-di-t-butyl-fluorenyl,5,8-di-trimethylsilyl-fluorenyl, 5,8-di-benzyl-fluorenyl,5,8-di-phenyl-fluorenyl and 5,8-di-naphthyl-fluorenyl.

[0029] Where the chromium catalyst precursor binds to more than oneheteroatom present on the support, it is, of course, possible for onechromium: support heteroatom bond to be formed in a vacant chromiumcoordination site whilst the other chromium: support heteroatom bond isformed via displacement of a leaving group present in the catalystprecursor.

[0030] The bonds between the heteroatoms present on the catalyst supportand the chromium catalyst preferably form directly from the chromiumatom, i.e. a chromium atom to heteroatom bond. The chromium atom may bein any convenient oxidation state, e.g. 1 to 4 or 6, especially 3, 4 or6.

[0031] Particularly preferred chromium catalyst precursors includeCr(allyl)₃, tris(2-methyl allyl) chromium, CrCp′₂, O₂CrCl₂,O₂Cr(OSiR′₃)₂ wherein Cp′ represents an unsubstituted cyclopentadienylgroup and R′ represents an optionally substituted alkyl, aryl or alkenylgroup, e.g. phenyl, tertbutyl, methyl, isopropyl, octenyl, ethyl,1,1,2,2-tetramethylpropyl.

[0032] The terms “support” or “carrier” are used interchangeably hereinto mean any material capable of supporting catalytically activecompounds. The support material for use in the invention preferablycomprises an organic polymer, preferably an organic porous polymerprovided in the form of distinct particles. Preferably, the supportmaterial will comprise porous polymer particles optionally cross-linkedby physical or chemical means, for example using conventionalcross-linking agents, e.g. divinylbenzene. Preferred support materialsinclude acrylate polymer particles or styrene-divinylbenzene polymerparticles.

[0033] As used herein, the term “functionalised support” is used todefine any support which has been functionalised so as to carryheteroatoms on its surface capable of forming a chemical bond with thechromium catalyst precursor. Examples of suitable functionalisedsupports are therefore those which carry at least one XH groups in whicheach X is independently an organic group and H is an active hydrogenatom attached to a heteroatom in the organic group X, the heteroatomhaving at least one electron pair available for coordination to thechromium catalyst precursor. Suitable heteroatoms which may be presentin the organic group X are those of groups 15 and 16 of the PeriodicTable, preferably, O, P, S and N, particularly O.

[0034] Preferred functionalised supports for use in the invention arethose having a pK_(a)<30 , preferably <25, more preferably <20.Particularly preferred for use in the invention are organic polymersupports carrying —OH, —N(alkyl)H or —NH₂ groups. It is preferred if theOH groups are not directly attached to an aryl ring.

[0035] The use of functionalized organic polymer particles having labilehydrogens with pKa <20 (especially benzylic hydrogens, i.e. attached toa heteroatom attached to a carbon attached to a phenyl ring) as supportsfor Cr and optionally a metallocene, is novel and forms a further aspectof the present invention. Viewed from this aspect the invention providesa heterogeneous olefin polymerization catalyst comprising a particulateorganic polymer support having a pKa of less than 20, metallated with acatalytically effective amount of chromium.

[0036] Especially preferred for use in the invention are polymersupports comprising divinylbenzene cross-linked polystyrene particlesmodified to carry functional hydroxy groups. Functional groups availableas attachment sites may be introduced by conventional techniques, forexample using a functionalised monomer when preparing the co-polymer.Alternatively, functional groups may be introduced by appropriatemodification (e.g. chemical modification) of a non-functionalisedco-polymer. Functionalised supports for use in the invention may, forexample, be prepared in a manner analogous to that described byEllingsen et al., J. Chrom. 535:147, 1990.

[0037] The use of a polymeric support, as opposed to a conventionalsilica support, is also believed to give rise to polymers suitable foruse in electrical insulation applications. The use of silica particlesin a polymerisation catalyst may give rise to “cracks” in the eventualpolymer through which moisture or water may be able to seep. Suchpolymers are therefore not suitable to protect electrical cables andcannot act as insulators. The functionalised supports of the presentinvention are believed to give rise to polymers free from such cracksand therefore have wide spread applications in the field of electricalinsulation.

[0038] When the chromium catalyst is bound to the support via two ormore heteroatoms, the heteroatoms which bind to the chromium catalystprecursor may be attached to the functionalised support by separateorganic groups, or may be bound to two heteroatoms which form part ofthe same organic group, e.g. the hydroxyl groups present in a diol.

[0039] It has surprisingly been found that where the chromium catalystbinds to a diol present on the support surface, the resulting polymerpossesses a broad molecular weight distribution. Where the chromiumcatalyst binds to two heteroatoms present on separate organic groups,the resulting polymer is found to have a very narrow molecular weightdistribution. Without wishing to be limited by theory, it is believedthat by binding to heteroatoms present on separate organic groupspresent on the support surface the system has a greater flexibilitycompared to the case where the chromium catalyst is bound to the muchmore rigid diol system. It is believed that the greater flexibilitygives rise to a catalyst which allows production of a narrow molecularweight species.

[0040] In an especially preferred embodiment, the catalyst system of theinvention is employed in the manufacture of polymers having a narrowmolecular weight distribution which has not been possible using previouschromium catalysts systems such as CrO/SiO₂, CrCp2/SiO₂,silylchromate/SiO₂—Al₂ 0 ₃, Cr(allyl)₃/SiO₂, or Cr (cumene)₂/SiO₂—Al₂O₃.

[0041] Suitable organic groups XH include C₁₋₁₀ alcohols, especiallyC₁₋₆ alcohols, C₁₋₁₀ amines, especially C₁₋₆ amines, C₁₋₁₀ thiols,especially C₁₋₆ thiols, optionally substituted aryl groups carrying NH,OH or SH moieties, e.g. benzyl alcohol, phenol, aniline all preferablybound to the support by the 4-position of the benzene ring. Furthersuitable groups will be readily determined by the skilled artisan.

[0042] It is of course possible for the XH group to have two or moreheteroatoms and the chromium catalyst precursor may bind to one or bothheteroatoms on the same organic group. Suitable XH groups in this regardinclude diamines and diols such as (1,2-dihydroxyethyl) phenyl.

[0043] Where the XH group carries a single heteroatom and the chromiumcatalyst precursor has two sites available for binding heteroatoms it isobviously more likely that the chromium catalyst precursor will bond totwo heteroatoms on adjacent XH groups if there is a high surface densityof XH groups present on the support. If there is a low surface densityof XH groups then it is envisaged that the chromium catalyst precursorwill bind to a single XH group irrespective of whether it carriesfurther possible coordination sites. Such an arrangement is believed togive rise to low molecular weight oligomeric polymer products.

[0044] The terms “co-catalyst” and “activator” are used interchangeablyherein to define any compound or component which is capable ofactivating a chromium catalyst following attachment to the support. Theactivator compound should preferably be one capable of stabilising achromium catalyst without affecting its ability to function as acatalyst and must be sufficiently labile to permit displacement by anolefin monomer or other polymerisable species during polymerisation.Preferably the supported activator will be non-coordinating or weaklycoordinating towards the chromium.

[0045] Advantageously, the catalyst system herein described may be usedin the absence of co-catalyst. However, for certain systems, e.g. thosein which oxo or halogen groups are present in the chromium catalyst acocatalyst may be used. Suitable cocatalysts are well known and includealkyl aluminium compounds, in particular alumoxanes, and metal alkyls,e.g. Zn, Mg, Al or B alkyls. Suitable alumoxanes include C₁₋₁₀ alkylalumoxanes, e.g. methyl alumoxane (MAO) and isobutyl alumoxanes (e.g.tetra and hexaisobutyl alumoxanes, TIBAO and HIBAO), especially MAO.Alumoxane co-catalysts are described by Hoechst in WO-A-94/28034. Theseare linear or cyclic oligomers having up to 40, preferably 3 to 20,—[Al(R″)O]— repeat units (where R′ is hydrogen, C₁₋₁₀ alkyl, preferablymethyl, or C₆₋₁₈ aryl or mixtures thereof).

[0046] The supported catalyst of the invention may be prepared bycombining the functionalised support and the chromium catalyst precursorin a solvent.

[0047] Suitable solvents for use in the methods of the invention includealiphatic and alicyclic hydrocarbons such as isobutane, butane, pentane,hexane, heptane, cyclohexane, cycloheptane etc. and aromatic compoundssuch as benzene, toluene, xylene etc. Reactions are conveniently carriedout in an inert, moisture-free, oxygen-free environment due to thesensitivity of the catalyst components to moisture and oxygen.Preferably the addition of the chromium catalyst precursor to thesupport takes place at low temperature e.g. between −80 to 20° C.,preferably between −30 and 0° C., preferably −10° C. The supportedcatalyst system may readily be isolated by removing the solvent invacuo, by filtration or may be used directly in a slurry state fordirect use.

[0048] Where a cocatalyst is being employed this may conveniently beadded to the supported chromium catalyst system by standard procedures.For example, MAO may be added to the carrier in toluene.

[0049] The supported chromium catalysts herein described may be used topolymerise any olefin or mixture of olefins, for example optionallysubstituted C₂₋₃₀ α-olefins. C₂₋₈ α-olefins and mixtures thereof, e.g.C₂- or C₃-olefins, are particularly preferred. The process of theinvention is particularly suitable for the polymerisation of α-olefinssuch as ethylene, propylene, 1-butene, 1-pentene, 1-hexene,3-methyl-1-butene and 4-methyl-1-pentene, especially preferablyethylene.

[0050] The catalyst systems may be used in any polymerisation orpre-polymerisation process, e.g. gas, slurry or solution phase.Preferably, these will be used in gas or slurry phase reactors.Polymerisation according to the invention may be performed usingstandard polymerisation techniques and using conventional polymerisationreactors, e.g. loop reactors, gas phase reactors, or stirred tankreactors.

[0051] The polymerisation process of the invention is typicallyconducted in the presence of a diluent. As a diluent, a linear, branchedor cyclic saturated hydrocarbon such as isobutane may be used.

[0052] In a further embodiment the support may be impregnated with apolymerisation active metal complex/activator solution to give a dualsite catalyst which has one site which is sensitive to hydrogenconcentration and one site which is less sensitive to hydrogenconcentration. Such a catalyst species may allow the formation ofbimodal polymers in which depending on the nature of the functionalisedsupport very specific molecular weight distributions may be achieved.

[0053] The polymerisation active metal complex may be a complex carryingligands such as alkoxy groups, acetylacetonates, bis(alkylamidinate),etc. Such ligands are described by G. J. P. Britovsek et al, Angew.Chem. Int. Ed. 1999, 38, 428-447. Preferably however, the polymerisationactive metal complex is a metallocene catalyst. Metallocene catalystsfor use in this regard may be any conventional metallocene catalyst. Asused herein, the term metallocene is used to refer to all catalyticallyactive metal: η-ligand complexes in which a metal is complexed by one,two or more open chain or closed ring η-ligands. The use of bridgedbis-η-ligand metallocenes, single η-ligand “half metallocenes”, andbridged η-σ ligand “scorpionate” metallocenes is particularly preferred.The metal in such complexes is preferably a group 4 to 10 metal or alanthanide or actinide, especially a group 4, 5 or 6 metal, particularlyZr, Hf or Ti. The η-ligand preferably comprises an η⁴ or η⁵ open chainor an η⁵-cyclopentadienyl ring, optionally with a ring or chain carbonreplaced by a heteroatom (e.g. N, B, S or P), optionally substituted bypendant or fused ring substituents and optionally linked by bridge (e.g.a 1 to 4 atom bridge such as (CH₂)₂, C(CH₃) ₂ or Si(CH₃)₂) to a furtheroptionally substituted homo or heterocyclic cyclopentadienyl ring. Thering substituents may for example be halo atoms or alkyl groupsoptionally with carbons replaced by heteroatoms such as O, N and Si,especially Si and O and optionally substituted by mono or polycyclicgroups such as phenyl or naphthyl groups. Suitable η-ligands, includethose of formula II discussed above. Examples of such homo orheterocyclic cyclopentadienyl ligands are well known in the art (seee.g. EP-A-416815, WO096/04290, EP-A-485821, EP-A-485823, U.S. Pat. Nos.5,276,208 and 5,145,819).

[0054] Besides the η-ligand, the metallocene complex used according tothe invention may include other ligands; typically these may be halide,hydride, alkyl, aryl, alkoxy, aryloxy, amide, carbamide or other twoelectron donor groups. Any hydrocarbyl ligand here will generallycontain up to 20 carbons, preferably up to 10 carbons, e.g. up to 6carbons.

[0055] The polymerisation active metal complex, e.g. metallocene isconveniently impregnated into the support after the chromium catalystprecursor has been bound to the support surface. Preferably, thepolymerisation active metal complex is added to the dried supportcomplex in toluene optionally in the presence of a cocatalyst, e.g. MAO.After impregnation the final supported catalyst system may beconveniently dried in vacuo or may be used kept in a slurry state fordirect use.

[0056] The supported catalysts are most usefully employed in either gasor slurry phase processes, both of which are well known in the art. Thetemperature of the polymerisation reaction will typically be in therange of from 0 to 300° C., preferably from 60 to 120° C. The pressureemployed for the olefin or olefins is typically from 1 to 2000 bars,preferably from 5 to 20 bars. The residence time is generally from 1minute to 20 hours, preferably from 0.5 to 6 hours.

[0057] For slurry reactors, the reaction temperature will generally bein the range 60 to 1100° C. (e.g. 85-110° C.), the reactor pressure willgenerally be in the range 5 to 80 bar (e.g. 25-65 bar), and theresidence time will generally be in the range 0.3 to 5 hours (e.g. 0.5to 2 hours). The diluent used will generally be an aliphatic hydrocarbonhaving a boiling point in the range −70 to +100° C., especiallyisobutane.

[0058] For gas phase reactors, the reaction temperature used willgenerally be in the range 60 to 115° C. (e.g. 70 to 110° C.), thereactor pressure will generally be in the range 10 to 25 bar, and theresidence time will generally be 1 to 8 hours. The gas used willcommonly be a non-reactive gas such as nitrogen together with monomer(e.g. ethylene or propylene and/or other comonomers).

[0059] It is within the scope of the application to employ the supportedcatalyst as hereinbefore described together with another catalyst, e.g.a metallocene catalyst, Ziegler catalyst, etc. It is preferred howeverto employ the supported chromium catalyst system of the invention in theabsence of other catalyst materials.

[0060] As previously mentioned, polyolefins produced by the supportedcatalyst system of the invention have tailorable molecular weightdistributions, e.g. M_(w)/M_(n)=1 to 100, preferably 3 to 80. Also, theproduct polyolefins have an MFR₂₁/MFR₂<200 and an MFR₂<50.

[0061] Moreover it has surprisingly been found that the electricalproperties of the polyolefins prepared using the supported catalystsystem of the invention are advantageous.

[0062] Pre-polymerisation of the supported catalyst of the invention maybe used for further control of the polymer particle morphology, e.g. intypical gas phase or slurry reaction processes.

[0063] The polymers produced in accordance with the invention may beformulated together with conventional additives, e.g. antioxidants,UV-stabilizers, colors, fillers, plasticizers, etc. and can be used forfibre or film extrusion or for raffia, or for pipes, or for cable orwire applications or for moulding, e.g. injection moulding, blowmoulding, rotational moulding, etc., using conventional moulding andextrusion equipment.

[0064] The invention will now be described further by way of thefollowing non-limiting Examples and figures.

BRIEF DESCRIPTION OF THE FIGURES

[0065]FIG. 1 depicts the IR spectra of the polymer produced with the(nBuCp)₂ZrCl₂/MAO/Support A (Example 9 —Catalyst X) and the two combinedCatalysts VIII and IX (Examples 7 and 8), all produced at 38 bar totalpressure and 1.0 bar H₂ from the start.

[0066]FIG. 2 depicts the GPC traces of polymers produced withCr(2-Me-allyl)₃/E-110 (Catalyst IX) and with(nBuCp)₂ZrCl₂/MAO/Cr(2-Me-allyl)₃/E-110 (Catalyst VIII) with high andlow Cr/Zr loading.

EXAMPLE 1

[0067] Preparation of trisallyl-chromium and tris(2-methyl-allyl)chromium

[0068] A Schlenck flask containing CrCl₃ was heated under vacuum by theuse of a gas flame before starting the reaction. To a slurry of CrCl₃(0.90 g, 5.68 mmol) in 20 ml ether at −30° C. was added allylmagnesiumbromide (or 2-methylallylmagnesium bromide) (50 ml, 18.5 mmol, as a0.369 M ether solution) dropwise over a period of 2 hrs. Stirring wascontinued for another 3 hrs at −30° C. and overnight at −70° C. Theinorganic magnesium salts were removed by filtration (washed with 25 mlether) at −30° C., and all volatiles were removed under reducedpressure. The product was extracted in pentane (50+25 ml) at −20° C. andfiltrated. Yield: 72.6% based on Cr-analysis (ICP-AES).

EXAMPLE 2

[0069] Preparation of supported tris(2-methylallyl)chromium

[0070] Two supports were used to support tris(2-methylallyl)-chromium.Support A is a p-hydroxymethylstyrene-co-divinylbenzene polymer preparedby copolymerising p-hydroxymethylstyrene and divinylbenzene as describedby Ellingsen et al., J. Crom. 535 (1990) 147. The particles formed, hasa degree of crosslinking of 60%, a porosity of 75% and an averageparticle diameter of 30 microns. The amount of available hydroxy groupswas measured by reacting 100 mg of the support with tert-butyl-lithiumat −30° C. in a known volume of pentane, distilling the volatiles into aseparate Schlenck bottle and measuring the amount of isobutane formed byGC analysis. 1.2 mmol OH/g support was measured for Support A.

[0071] Support B is ap-(1,2-dihydroxyethyl)styrene-co-styrene-co-divinylbenzene polymerprepared by copolymerising p-(1,2-dihydroxyethyl)styrene, styrene anddivinylbenzene in a similar manner as for Support A. The particlesformed, has a degree of crossbinding of 71%, a porosity of 70% and anaverage particle diameter of 30 microns. The amount of hydroxy groupsmeasured was 0.80 mmol OH/g.

[0072] Thus, for Support A, the two allyl ligands of the complex mayreact with two OH groups and form a polymerising chromium site accordingto the reaction:

[0073] The following supported catalysts were been prepared:

[0074] Preparation of Catalyst I:

[0075] 0.230 g washed and dry Support A containing 0.276 mmol OH groupswere suspended in 15 ml cyclohexane. 2.4 ml (0.138 mmol) of a pentanesolution of Cr(2-Me-allyl)₃ containing 4.8 mg Cr/g solution was thenadded at −10° C. The solution was stirred for 30 minutes. The colour ofthe suspension turns greenish. The solution was allowed to warm toambient temperature and the solvent was removed under reduced pressureyielding a light green powder.

[0076] For Support B, the two allyl ligands of the chromium complex mayreact with two OH groups of one 4-(1,2-dihydroxyethyl)phenyl group or OHgroups from two such groups on the support.

[0077] Preparation of Catalyst II:

[0078] 1.56g Support B containing 0.40 mmol diol/g was suspended in 25ml pentane and cooled to −30° C. Then 7.34 ml of a pentane solutioncontaining 0.085 mmol Cr(2-Me-allyl)₃/ml was added by using a syringe.The suspension was stirred at −30° C. for about 30 minutes. The colourturns dark. The suspension was then warmed to ambient temperature whilestirring for another 30 minutes before it was filtrated yielding acolourless filtrate and a greenish powder. The solid is dried well underreduced pressure. Yield: 1.50 g, stored in the glove box.

EXAMPLE 3

[0079] Ethylene polymerisations have been carried out with theallyl-chromium-based catalysts prepared in Examples 1 and 2. Thepolymerisation conditions and the results from these are given in Table1 and 2 below. TABLE 1 Polymerisation conditions and activity data frompolymerisations with heterogeneous catalysts based on Cr(2-Me-allyl)₃.Catalyst I uses a benzyl alcohol functionalised carrier (Support A)while Catalyst II uses a diol functionalised carrier (Support B).Polyrnerisations in a 1-litre autoclave with 0.5-1 isobutane as diluentat 38 bar total pressure, 90° C. 1- Amount Activity H₂ Hexene Catalysttime Yield g poly./ Catalyst bar ml mg min PE/g gcat./hour I 0 0 100 8525.9 183 II 1.0 0 200 30 54.5 545

[0080] TABLE 2 Characteristics of polymer produced with heterogeneoussingle site catalysts based on Cr(2-Me- allyl)₃. Polymerisations in a1-litre autoclave with 0.5-1 isobutane as diluent at 38 bar totalpressure 90° C. HLMI Density Cat g/10 min HLMI/MI g/cm³ Mw Mw/Mn I noflow — 0.935 595000 3.2 II 16.7 835 0.948 380000 114

[0081] The MWD for the product produced using Catalyst II is very broadwith Mn=3300, Mw=380000 and Mw/Mn=114. The MWD curve has a low molecularweight tail giving most of the broadness. When a benzylalcoholfunctionalised carrier is used, i.e. using Catalyst I, a narrow MWD isobtained with Mw/Mn=3.2. In both cases the morphology of the polymerformed is excellent.

EXAMPLE 4

[0082] Triphenylchromate was reacted with a phenol functionalisedcarrier, Support C as described below:

[0083] Support C is a p-vinylphenol-co-styrene-co-divinylbenzenecopolymer made analogously to Support A by copolymerising p-vinylphenol,styrene and divinylbenzene. The particles formed have an averageparticle diameter of 30 microns.

[0084] Preparation of Catalyst III:

[0085] 1.50 g Support C containing 0.56 mmol OH/g was suspended in 50 mltoluene. 183 mg (Ph₃SiO)₂CrO₂ (to give 1.0 wt % Cr) was added and thesuspension was refluxed overnight at 1.30° C. After cooling to ambienttemperature, the suspension was filtrated. The solid was dried underreduced pressure yielding and stored in the glove box.

[0086] A catalyst activated with MAO was prepared:

[0087] Preparation of Catalvst IV:

[0088] 0.730 g Catalyst III was added to a 50 ml round-neck bottle underargon atmosphere together with a magnetic stirrer. Assumes a pore volumeof 1.5 ml/g. 1.0 ml MAO/toluene (13.1 wt % Al) is added by using asyringe while stirring the powder giving a Al/Cr molar ratio of about30. After about 30 minutes stirring the sample is dried under poorvacuum and stored in the glove box.

[0089] A number of polymerisation tests were carried out with thesecatalysts. The polymerisation conditions and results are given in Table3 below. TABLE 3 Results from polymerisations with heterogeneouscatalysts based on (Ph₃SiO)₂CrO₂ on Support C (1.0% Cr). Polymerisationsin a 1-litre autoclave with 0.5-1 isobutane as diluent at 38 bar totalpressure, 90° C. m_(cat) time Yield Activity M1 HLMI HLMI DensityCatalyst H₂ mg min g g/(gcat.h) g/10 min MI g/cm³ IV 0 309 110 13.1 23 —0.02 — 0.950 IV 1.0 405 70 10.4 22 0.055 11.8 215 — IV 1.0 330 103 9.717 0.22  29.3 133 0.947

[0090] The sensitivity towards hydrogen as a chain termination agentappears large, contrary to what would be expected for conventionalchromium catalysts.

EXAMPLE 5

[0091] Preparation of Catalyst V:

[0092] 1.00 g Support B containing 0.40 mmol diol/g was suspended in 30ml toluene. 32.4 μl Cl₂CrO₂ was added and the suspension was stirred atambient temperature for one hour. The suspension was filtrated yieldinga colourless filtrate and a darkish powder. The solid was washed twicewith 20 ml portions of pentane, then dried under reduced pressureyielding 1.10 g light brown powder with theoretically 2.0 wt % Cr.

[0093] MAO was introduced by the following procedure:

[0094] Preparation of Catalyst VI:

[0095] 0.500 g Catalyst V was added to a Schlenck tube under argonatmosphere. 0.89 ml MAO/toluene was added dropwise using a syringe whilestirring. After 30 minutes stirring and shaking, the tube was evacuatedby using a vacuum, then introduced to the glove box. Yield 0.92 g lightbrown powder. TABLE 4 Results from polymerisations with Catalyst V andVI. Polymerisations in a 1-litre autoclave with 0.5-1 isobutane asdiluent at 38 bar total pressure, 90° C. m_(cat) time Yield PE ActivityM1 HLMI HLMI Density Catalyst H₂ mg min g g/(gcat.h) g/10 min g/10 minMI g/cm³ V* 1.0 206 100 17.8 52 — — — — VI 1.0 460 60 30.0 65 3.9 300 77 >0.96 VI 1.0^(†) 394 60 32.3 82 4.48 455 102 0.933

EXAMPLE 6

[0096] Preparation of Catalyst VII:

[0097] 0.565g of Catalyst II prepared as in Example 2 was added to aSchlenck tube under argon atmosphere together with a magnetic stirrer.In a separate Thomas bottle 5 mg (nBuCp) ₂ZrCl₂ (12.4 μmol) was stirredwith 2.1 ml MAO/toluene (13.1 wt % Al). 0.68 ml of this solution is thenadded by syringe to a dry sample of Catalyst II while stirring. Afterabout 20 minutes stirring the sample is dried under vacuum and stored ina glove box. Yield 1.1 g.

EXAMPLE 7

[0098] Preparation of Catalyst VIII:

[0099] 0.420 g of Catalyst II prepared as in Example 2 was added to aSchlenck tube under argon atmosphere together with a magnetic stirrer.In a separate Thomas bottle 5.5 mg (nBuCp)₂ZrCl₂ was stirred with 9.1 mlMAO/toluene (13. 1 wt % Al). 0.50 ml of this solution was then added bysyringe to a dry sample of Catalyst II while stirring. After about 30minutes stirring the sample was dried under vacuum and stored in theglove box. Yield 0.89 g.

Example 8

[0100] Preparation of Catalyst IX:

[0101] 0.920 g of Catalyst II prepared as in Example 2 was added to aSchlenck tube under argon atmosphere together with a magnetic stirrer.In a separate Thomas bottle 14 mg (nBuCp)₂ZrCl₂ was stirred with 8.2 mlMAO/toluene (13.1 wt % Al) and another 33.4 ml toluene for about 30minutes. 1.1 ml of this solution was then added by syringe to a drysample of Catalyst II while stirring. After about 30 minutes stirringthe sample was dried under vacuum and stored in the glove box. Yield1.88 g.

EXAMPLE 9

[0102] As a reference catalyst a single site catalyst based on(nBuCp)₂ZrCl₂/MAO without the chromium component was prepared:

[0103] Support D is an unfunctionalised styrene-co.-divinylbenzenecopolymer made in a similar fashion to Support A above by copolymerisingstyrene and divinylbenzene. The particles formed have a degree ofcross-binding of 80%, a porosity of 70% and an average particle diameterof 30 microns.

[0104] Preparation of Catalyst X:

[0105] 2.04 g of Support D was added to a Schlenck tube under argonatmosphere together with a magnetic stirrer. In a separate Thomas bottle5.5 mg (nBuCp)₂ZrCl₂ was stirred with 9.1 ml MAO/toluene (13.1 wt % Al)for about 30 minutes. 2.45 ml of this solution is then added by syringeto the dry sample of Support D while stirring. After about 30 minutesstirring the sample is dried under vacuum and stored in a glove box.Yield 4.1 g. Al/Zr=2800.

EXAMPLE 10

[0106] Ethylene Polymerization

[0107] Ethylene was polymerized using the catalysts of Examples 6 to 9.Details are set forth in Tables 5 and 6 below. TABLE 5 Catalystparameters for the catalysts of Examples 6 to 9: Catalyst wt % Cr wt %Zr Cr/Zr* Al/Cr* Al/Zr* II 2.0  — — — — VII 1.03 0.033   55 13  718 VIII0.94 0.0077 215 13 2800 IX 0.98 0.0049 350  5 1000 X — 0.0082 — — 2800

[0108] TABLE 6 Polymerisation conditions and activity data frompolymerisations with heterogeneous catalysts of Examples 6 to 9.Polymerisations in a 1-liter autoclave with 0.5-L isobutane as diluentat 38 bar total pressure, 90° C. Catalyst H₂ 1-Hex m_(cat) time Yield PEActivity Metal Run No bar ml mg min g g/(g_(cat).h) Cr 11-1 1.0 0 200 3054.5 545 Cr/Zr VII-1 1.0 0 197 12 65.0 1650 Cr/Zr VII-2 1.0 0 134 1466.9 2140 Cr/Zr VII-3 1.0 10 95 15 68.7 2893 Cr/Zr VII-4 1.0 10 66 43193.5 4091 Cr/Zr VIII-1 0 0 154 30 87.3 1134 Cr/Zr VIII-2 1.0 0 95 6029.1 306 Cr/Zr VIII-3 1.0 10 125 60 42.0 336 Cr/Zr IX-1 0 0 373 45 92.3330 Cr/Zr IX-2 1.0 0 345 45 85.1 329 Cr/Zr LX-3 1.0 10 305 60 93.4 306Zr X-1 0 0 152 45 84.4 740 Zr X-2 1.0 0 145 30 96.7 1334 Zr X-3 1.0 10145 45 36.8 338 Characteristics of polymer produced with heterogeneouscatalysts of Examples 6 to 9. Polymerisations in a 1-litre autoclavewith 0.5-L isobutane as diluent at 38 bar total pressure 90° C. CatalystMI HLMI HLMI Density M_(w) M_(w) Run No. g/10 min g/10 min MI g/cm² /10³M_(n) II-1 0.02 16.7 835 0.948 380 114 VII-1 238 — — 0.945 — — VII-2 330— — >0.96 — — VII-3 420 — — >0.96 — — VIII-1 0.12 3.2 27 0.941 245 2.8VIII-2 1600 — — >0.96 — — VIII-3 1400 — — >0.96  41 28 IX-1 0 0.046 —0.935 1112  28 IX-2 0.017 2.43 143 0.946 — — IX-3 0.022 2.31 105 0.945370 85 X-1 0.18 4.2 23 0.937 — — X-2 2.75 158 61 0.960 — — X-3 5000 —— >0.96 — —

[0109] The IR spectra of selected polymers in the region 850 to 1050 nmare shown in FIG. 1. The morphology of all polymers produced wasexcellent.

1. A supported chromium catalyst-system comprising a chromium catalystbound via at least one heteroatom to a functionalised support, saidheteroatom being connected to said support via an organic group whereinsaid chromium catalyst is derived from (i) a compound of formula (I)CrA_(x)B_(y)  (I) wherein each A independently represents an η-ligand;each B independently represents halogen, alkenyl, siloxy, alkyl, alkoxy,amido or cyclopentadienyl; x is an integer of 1 or 2; and y is aninteger of 1 to 2 wherein x+y=3; (ii) a compound of formula (II)CrD₄  (II) wherein each D independently represents alkyl, siloxy,alkoxy, oxo, halo or aryl; or (iii) a compound of formula Cr(η-ligand)₂or CrD(ηn-ligand) wherein D represents alkyl, siloxy, alkoxy, oxo, haloor aryl.
 2. A catalyst system as claimed in claim 1 wherein saidchromium catalyst precursor is Cr(allyl)₃ tris-(2-methyl allyl)chromium, CrCp′₂ O₂CrCl_(2, O) ₂Cr(OSiR′₃)₂ wherein Cp′ represents anunsubstituted cyclopentadienyl group and R′ represents phenyl,tertbutyl, methyl, isopropyl, octenyl, ethyl or1,1,2,2-tetramethylpropyl.
 3. A catalyst system as claimed in any one ofclaims 1 to 2 wherein said support comprises acrylate polymer particlesor styrene-divinylbenzene polymer particles.
 4. A catalyst system asclaimed in any one of claims 1 to 3 wherein said support comprises atleast one group Xθ wherein X represents an organic group comprising saidheteroatom.
 5. A catalyst system as claimed in claim 4 whereinXθrepresents a deprotonated C₁₋₁₀ alcohol, C₁₋₁₀ amine, C₁₋₁₀ thiol, anaryl group bound to an NH, SH or OH group, C₁₋₁₀ diol or C₁₋₁₀ diamine.6. A catalyst system as claimed in claim 5 wherein Xθcomprises adeprotonated OH, —N(alkyl)H or —NH₂ groups.
 7. A catalyst system asclaimed in claim 8 wherein Xe represents a deprotonated benzyl alcoholor 1,2-dihydroxyethyl phenyl.
 8. A catalyst system as claimed in claim10 wherein the benzyl alcohol or 1,2-dihydroxyethyl phenyl group isbound. to the support via the 4-position on the phenyl ring.
 9. Acatalyst system as claimed in any one of claims 1 to 8 wherein saidsupport has impregnated therein a further polymerisation active metalcomplex.
 10. A process for the preparation of a supported chromiumcatalyst system as claimed in any one of claims 1 to 9 comprising: (I)reacting a chromium (i) compound of formula (I) CrA_(x)B_(y)  (I)wherein each A independently represents an η-ligand; each Bindependently represents halogen, alkenyl, siloxy, alkyl,. alkoxy, amidoor cyclopentadienyl; x is an integer of 1 or 2; and y is an integer of 1to 2 wherein x+y=3; (ii) a compound of formula (II) CrD₄   (II) whereineach D independently represents alkyli siloxy, alkoxy, oxo, halo oraryl; or (iii) a compound of formula Cr(η-ligand) ₂ or CrD(η-ligand)wherein D represents alkyl, siloxy, alkoxy, oxo, halo or aryl with afunctionalised support in a solvent to bind said compound to saidfunctionalised support via at least one heteroatom attached to saidsupport via an organic group; and (II) recovering a supported catalystprecursor as a free-flowing solid or slurry.
 11. A process as claimed inclaim 10 further comprising the step of impregnating said support with apolymerisation active metal complex, between steps (I) and (II).
 12. Aparticulate organic polymer support having a pKa of less than 20,metallated with a catalytically effective amount of chromium.
 13. Theuse of a supported catalyst system as claimed in any one of claims 1 to8 or 12 in the polymerisation of olefins.
 14. A process ofpolymerisation comprising polymerising at least one olefin in thepresence of a supported catalyst system as claimed in any one of claims1 to 8 or
 10. 15. A process as claimed in claim 14 which takes place inthe absence of a cocatalyst.
 16. A process as claimed in claim 14wherein a cocatalyst is employed.
 17. Polyolefins prepared using acatalyst system as claimed in any one of claims 1 to 8 or 10.